The present invention relates to a light conversion device absorbing light in a region ranging from a near ultraviolet ray to a visible ray from a light source to perform conversion into a visible ray having a predetermined wavelength (color), and more particularly, to a light conversion film including an organic fluorescent dye and a light conversion device including the light conversion film.
Generally, a fluorescent material is a light emission material absorbing energy in a form such as light or electricity from the outside to emit light having an intrinsic wavelength, and may be classified into an inorganic fluorescent material, an organic fluorescent dye, a nano-crystal fluorescent material, and the like according to a component constituting the fluorescent material and a light emission mechanism. Recently, various efforts for modifying a spectrum of the light source by using the fluorescent materials have been made, due to the above efforts, a portion of a predetermined wavelength of light emitted from the light source is absorbed by the fluorescent material and is converted into light having a longer wavelength in a visible ray region to be emitted, and brightness, color purity, and color reproducibility of emitted light, and the like may be largely improved according to a light emission property of the fluorescent material.
Since the inorganic fluorescent material is constituted by a mother substance such as sulfides, oxides, and nitrides and an activator ion, has excellent physical and chemical stabilities, and may be reproduced with high color purity, the inorganic fluorescent material may be applied to a high-quality display apparatus, but there are drawbacks in that the fluorescent material is very expensive, light emission efficiency is low, and particularly, there is a limit in development of the fluorescent material excited in a near ultraviolet ray or blue region of 400 nm or more to emit light.
A fluorescent wavelength of the nano-crystal fluorescent material formed of Group II-IV or III-V semiconductor particles having a size of several nanometers is changed according to a particle size unlike the organic fluorescent dye. As the particle size is reduced, light having a short wavelength is emitted, and the nano-crystal fluorescent material may represent all visible ray regions having a desired wavelength by adjusting the size. Further, since a light absorption coefficient is 100 to 1000 times larger than that of a general organic dye and quantum efficiency is higher than that of the general organic dye, very strong fluorescence occurs, and particularly, only transition from a ground vibration state of a conduction band to a ground vibration state of a valence band is observed, and thus the fluorescent wavelength exhibits almost monochromatic light, but there are drawbacks in that it is difficult to secure price competitiveness due to a high raw material cost, and particularly, the fluorescent material is weak to heat, oxygen, or the like.
On the other hand, the organic fluorescent dye has merits in that as compared to the inorganic fluorescent material, various light emission spectra are present, quantum efficiency is excellent, and particularly, costs are low, and thus a value to be used as a light conversion device is sufficient. However, the concentration should be increased in order to increase conversion efficiency of light passing through the organic fluorescent dye and the intensity of converted light. In this case, it is known that an extinction phenomenon by the concentration cannot be avoided, and particularly, stability to heat or light is reduced, and thus it is necessary to maximize light emission efficiency and stably maintain a light emission property by using a more stable organic or inorganic material to protect the organic dye. As a method of stabilizing the organic dye, a method of improving light stability of the fluorescent dye in an aqueous solution by using cucurbiturils to form a cucurbituril-dye complex is proposed.